The present disclosure relates to a method and a device for reducing the humidity of a gas in a housing interior, in particular in a battery housing interior.
The method and the device are preferably to be used for reducing the humidity of housing interiors, in which battery cells or batteries are arranged. Battery cells and batteries which are assembled from battery cells form, as is known, one or more accumulators which can be charged electrically and can be discharged again. Here, a battery cell is a single galvanic cell which supplies a characteristic voltage depending on the combination of the materials of the electrodes of the cell. Connected to one another in series or in parallel, the battery cells can form a battery.
In particular, lithium-ion batteries have been used recently increasingly in mobile radio devices, laptops and other portable, electronic devices. Moreover, the use of lithium-ion batteries as energy stores in motor vehicles which are to be driven electrically is rising more and more. In order to ensure sufficient operational reliability and power provision, the lithium-ion batteries are to be operated here in an optimum temperature range, for which reason one or more cooling systems are often arranged in the immediate vicinity of the batteries in order to cool the batteries. Said cooling systems are usually likewise arranged in a housing which encloses the batteries or battery cells. The housing assumes the functions of fastening, protecting the sealing effect with respect to the environment, and insulating the batteries electrically. Moreover, in addition to the battery modules and the cooling system which is configured as a thermal management system, power electronics and electric lines for controlling the batteries during the charging and discharging operations are usually arranged in the battery housing. On account of the size of a battery housing, a device for equalizing the pressure is required, since otherwise excessively pronounced loadings can occur in the case of pressure differences.
In housings with an enclosed air volume which are exposed to temperature and/or volumetric changes, membranes which are composed of Teflon or at least comprise Teflon have been used up to now as pressure equalization elements. Although a membrane of this type keeps out liquids such as water, it is permeable for water vapor. Accordingly, in a humid external atmosphere humid air can penetrate into the housing. In the case of cooled regions within the housing, such as cooling devices as thermal management systems for setting an optimum battery operating temperature, condensation of the air humidity can accordingly occur within the housing. The condensation water which accumulates during the condensation can lead to short circuits of the electronics accommodated in the housing and/or to corrosion of components.